Photochromic naphthacenequinones, process for their preparation and the use thereof

ABSTRACT

Compounds of formula I or V or mixtures thereof ##STR1## wherein R is unsubstituted C 6  -C 14  aryl or C 6  -C 14  aryl which is substituted by C 1  -C 12  alkyl, C 1  -C 12  alkoxy, C 1  -C 12  alkylthio, phenyl, benzyl, --CN, --CF 3 , halogen or --COOR 5 , and R 5  is H, C 1  -C 18  alkyl, cyclohexyl, cyclopentyl, phenyl, C 1  -C 12  alkylphenyl, benzyl or C 1  -C 12  alkylbenzyl, and at least one of the substituents R 1  to R 4  is --F, --Cl or --Br, or is independently the group RO--, and the other substituents R 1  to R 4  are H, --F, --Cl or --Br, are reversible photochromic systems which can be used for contrast formation, light absorption or for the reversible optical storage of information.

This is a divisional of Ser. No. 07/801,150, filed Dec. 2, 1991, nowU.S. Pat No. 5,208,354.

The present invention relates to naphthacene-6,11- andnaphthacene-5,12-diones which are substituted in positions 5,12 and 6,11by aryloxy groups, and in positions 2, 3, 8 and/or 9 by at least onephenoxy group or at least one fluorine, chlorine or bromine atom, tocorresponding 5,12- and 6,11-dichloronaphthacenediones, to a process fortheir preparation and to the use thereof as photochromic systems forcontrast formation, light absorption or for recording information.

In Zhurnal Organicheskoi Khimii, Vol. 7, No. 11, pp. 2413-2415 (1971),Yu. E. Gerasimenko et al. describe 6-phenoxynaphthacene-5,12-dione as areversible photochromic compound which, when subjected to irradiationwith light, forms the orange 5-phenoxynaphthacene-6,12-dione(anaquinone). In Zhurnal Organicheskoi Khimii, Vol. 16, No. 9, pp.1938-1945 (1980), Yu. E. Gerasimenko et at. describe6,11-diphenoxynaphthacene-5,12-dione, whose photoisomerisation is usedfor synthesising 6-amino derivatives of12-phenoxynaphthacene-5,11-dione.

In one of its aspects, the present invention relates to compounds offormula I, or mixtures thereof, ##STR2## wherein R is unsubstituted C₆-C₁₄ aryl or C₆ -C₁₄ aryl which is substituted by C₁ -C₁₂ alkyl, C₁ -C₁₂alkoxy, C₁ -C₁₂ alkylthiol, phenyl, benzyl, --CN, --CF₃, halogen or--COOR₅, and R₅ is H, C₁ -C₁₈ alkyl, cyclohexyl, cyclopentyl, phenyl, C₁-C₁₂ alkylphenyl, benzyl or C₁ -C₁₂ alkylbenzyl, and at least one of thesubstituents R₁ to R₄ is --F, --Cl or --Br, or is independently thegroup RO--, and the other substituents R₁ to R₄ are --H, --F, --Cl or--Br.

R in formula I is preferably unsubstituted or substituted C₆ -C₁₀ arylsuch as phenyl, or 1-or 2-naphthyl. Preferably R is unsubstitued orsubstituted phenyl.

The group R may be substituted by one or more, preferably by 1 to 3,substituents. If R is substituted by alkyl, alkoxy or alkylthiol, theseradicals may be linear or branched and preferably contain 1 to 6, mostpreferably 1 to 4, carbon atoms. Exemplary of such radicals are methyl,ethyl, the isomers of propyl, butyl, pentyl, hexyl, heptyl, octyl,nonyl, decyl, and the corresponding alkoxy and alkylthio radicals.Preferred radicals are methyl, ethyl, n- and isopropyl, n-, iso- andten-butyl, methoxy, ethoxy, methylthio and ethylthio.

If R is substituted by halogen, preferred halogens are bromo, chloro andfluoro.

R₅ as alkyl may be linear or branched. Further examples of the alkylradicals mentioned above are the isomers of tridecyl, tetradecyl,pentadecyl, hexadecyl, heptadecyl and octadecyl. R₅ as alkyl preferablycontains 1 to 12, most preferably 1 to 6, carbon atoms. R₅ asalkylphenyl is preferably C₁ -C₆ alkylphenyl, most preferably C₁ -C₄alkylphenyl, for example dodecylphenyl, octylphenyl, hexylphenyl, n-,iso- or tert-butylphenyl, n- or iso-propylphenyl, ethylphenyl ormethylphenyl. R₅ as alkylbenzyl is preferably C₁ -C₆ alkylbenzyl, mostpreferably C₁ -C₄ alkylbenzyl, for example dodecylbenzyl, octylbenzyl,hexylbenzyl, n-, iso- or tert-butylphenyl, n- or isopropylbenzyl,ethylbenzyl or methylbenzyl. R₅ is preferably H or C₁ -C₁₈ alkyl, mostpreferably C₁ -C₁₂ alkyl.

In a preferred embodiment of the invention, R in formula I isunsubstituted or substituted by C₁ -C₄ alkyl, C₁ -C₄ alkoxy, C₁ -C₄alkylthio, --F, --Cl, --Br or --COOR₅, and R₅ is H or C₁ -C₁₈ alkyl.

In a particularly preferred embodiment of the invention, R in formula Iis --COO(C₁ -C₆)alkyl which is unsubstituted or substituted by --Cl or--Br.

Another preferred embodiment of the invention relates to those compoundsof formula I, wherein at least one of the substituents R₁ to R₄ is agroup RO-- or --F, --Cl or --Br, and the other substituents R₁ to R₄ are--H.

In yet a further preferred embodiment of the invention, R₁ or R₄, or R₁and R₃ or R₄, or R₁ and R₂, or R₁ to R₄ are a group RO--, --F, --Cl or--Br, most preferably a group RO-- or Cl.

Preferred compounds of formula I are those wherein R is unsubstitutedphenyl.

Particularly preferred compounds of formula I are6,11-diphenoxy-2-chloronaphthacene-5,12-dione,2,6,11-triphenoxynaphthacene-5,12-dione,6,11-diphenoxy-2,3,8,9-tetrachloronaphthacene-5,12-dione and2,3,6,8,9,11-hexaphenoxynaphthacene-5,12-dione.

In another of its aspects, the invention relates to a process for thepreparation of compounds of formula I, which comprises reacting 1 mol ofa compound of formula II ##STR3## wherein at least one of thesubstituents X is --F, --Cl or --Br, and the other substituents X are--H, --F, --Cl or --Br, in the presence of a polar aprotic solvent andat elevated temperature, with at least 2 mol of a compound of formulaRO.sup.⊖ M.sup.⊕, wherein R is as previously defined and M is an alkalimetal or tertiary ammonium containing 3 to 18 carbon atoms.

Surprisingly, it has been found that both chlorine atoms can besubstituted regioselectively by phenoxy groups even if the naphthaceneting system contains further halogen atoms.

The process of the invention is preferably carried out in thetemperature range from 50° to 200° C., most preferably from 50° to 150°C. The salts of formula RO.sup.⊖ M.sup.⊕ may be used as such or producedin situ in the reaction mixture by reacting a suitable phenol with analkali metal base or an alkali metal carbonate. The salts can be used inequimolar amounts or in excess, for example in an excess of up to 40 mol%, if it is desired to effect substitution of all halogen atoms.

Typical examples of suitable solvents are N-substituted carboxamides andlactams (such as dimethyl formamide or N-methylpyrrolidone), sulfoxidesand sulfones (such as dimethyl sulfoxide, tetramethylene sulfone), orethers (such as n-dipropyl ether, n-dibutyl ether, tetrahydrofuran ordioxane).

The compounds of formula I can be isolated and purified by conventionalmethods, for example by crystallisation and recrystallisation, or bychromatographic methods.

The compounds of formula RO.sub.⊖ M.sup.⊕ are known or obtainable inknown manner by reacting suitable phenols with alkali metal bases,alkali metal carbonates or tertiary amines. They can also be produced inthe reaction mixture in situ. Particularly suitable alkali metal cationsare Li.sup.⊕, Na.sup.⊕ and K.sup.⊕. Tertiary ammonium is typicallytrimethylammonium, triethylammonium, tri-n-propylammonium andtri-n-butylammonium.

The invention further relates to compounds of formula II ##STR4##wherein at least one of the substituents X is --F, --Cl or --Br, and theother substituents X are --H, --F, --Cl or --Br. The preferred meaningsof X are the same as those given for R₁ to R₄ defined as --H, --F, --Cland --Br in the compounds of formula I.

The compounds of formula II are obtainable by the following process:

The reaction of the known compounds of formula III ##STR5## wherein X isas defined in formula II, with a chlorinating agent, typically POCl₃,gives the compounds of formula IV which, when unsymmetricallysubstituted, are obtained as a mixture of position isomers of formulaeIV and IVa: ##STR6## These mixtures can be used direct for thepreparation of compounds of formula II or separated beforehand, forexample by chromatographic methods. The compounds of formula III areobtainable in a manner known per se for example, by reactingappropriately halogenated or non-halogenated phthalic anhydrides withappropriately halogenated or non-halogenated 1,4-dihydroxynaphthalene,in the presence of B₂ O₃, at elevated temperature.

The compounds of formula I are crystalline, thermally stable andlight-yellow to yellowish-orange in colour. They are soluble in organicsolvents. They are effective photoinitiators and photosensitisers forphotopolymerisable systems which contain ethylenically unsaturateddouble bonds. Further, the compounds of formula I are reversiblyphotochromic compounds which, when irradiated, undergo a marked colourchange from yellow to yellowish-orange to orange to red.

When the compounds of formula I are irradiated, alone or incorporated ina substrate, with light having a wavelength of ca. 300 to 450 nm, apronounced change in colour towards orange to red is observed. Incomparison with 6,11-diphenoxynaphthacene-5,12-dione, the lightabsorption is displaced to a higher wavelength. The change in colourderives from the photochemical conversion of the paraquinones of thisinvention into the corresponding anaquinones of formula V. The rate ofconversion is surprisingly high and, depending on the amount, thicknessof the sample and irradiation intensity, can be less than 3 seconds.

The invention further relates to the anaquinones of formula V ##STR7##wherein R, R₁, R₂, R₃ and R₄ are as previously defined, including thepreferred meanings.

The compounds of formula V can be obtained, after irradiating solutionsof the compounds of formula I, by removing the solvent, and, asrequired, purified by conventional methods.

The change in colour is reversible. Renewed irradiation with lighthaving a wavelength of ca. 450 to 550 nm gives the original colour(reformation of the paraquinone structure). It is especiallyadvantageous that this procedure can be repeated several times. Thestability of the photochemical conversion of paraquinones to anaquinonesand the reverse reaction to paraquinones is surprisingly high and thefatigue even in air or in substrates is correspondingly low. Thusvirtually no changes are observed in more than 200 cycles. It is alsoadvantageous that the light absorption necessary for the photochemicalconversion lies in the range of the wavelength of commercially availablelasers.

The invention further relates to the use of compounds of formula I or V,or mixtures thereof, as reversible photochromic structures for contrastformation or light absorption.

The compounds of formula I can be used as photoinitiators and,preferably, as photosensitisers in photopolymerisible systems, in whichcase they act simultaneously as colour indicators. Thus it is possibleto mark irradiated products (for example protective layers, printingplates, offset printing plates, printed circuits, solder masks) and todistinguish them from non-irradiated products and, in product control,to sort out imperfectly irradiated products before or after development.

The major advantage in using the compounds of formula I as colourindicators lies in the increase of the sensitiser action. Componentsnormally used as colour change systems generally effect a diminution ofthe photosensitivity.

The compounds of formula I or V can also be used by themselves, insolution or incorporated in polymers, as photochemically modifiablecolour indicators or as photochemically modifiable circuit components.

The compounds of formula I can also be used in organic or inorganicglass as photochemically modifiable colour filters, for example in glassfor sunglasses, contact lenses, windows and mirrors.

The invention further relates to a radiation-sensitive compositioncomprising

a) a radiation-sensitive organic material, and

b) at least one compound of formula I or V or a mixture thereof.

The compounds of formulae I and V or mixtures thereof may be present inan amount of 0.001 to 20% by weight, preferably 0.001 to 10% by weightand, most preferably, 0.01 to 5% by weight, based on component a).

Radiation-sensitive and hence also photostructurable materials areknown. They may be positive or negative systems. Such materials aredescribed, for example, by E. Green et al. in J. Macromol. Sci.; Revs.Macromol. and Chem., C21(2), 187-273 (1981 to 1982) and by G. A.Delzenne in Adv. Photochem., 11, S. 1-103 (1979).

The radiation-sensitive organic material is preferably al ) anon-volatile monomeric, oligomeric or polymeric substrate containingphotopolymerisable or photodimerisable ethylenically unsaturated groups,a2) a cationically curable system, or a3) photocrosslinkable polyimides.

Photopolymerisable substances are typically acrylates and, preferably,methacrylates of polyols, for example ethylene glycol, propanediol,butanediol, hexanediol, bis(hydroxymethyl)cyclohexane,polyoxyalkylenediols such as di-, tri- or tetraethylene glycol, di- ortri-1,2-propylene glycol, trimethylolmethane, trimethylolethane ortrimethylolpropane and pentaerythritol, which may be used by themselves,in mixtures and in admixture with binders.

Exemplary of photodimerisable substances are homo- and copolymers whichcontain cinnamic acid groups or substituted maleimidyl compounds in sidegroups or chalcone groups in the polymer chain.

Preferred compositions are those wherein component al) is a homo- orcopolymer of acrylates, methacrylates or maleates whose ester groupscontain a radical of formula ##STR8## wherein A is linear or branchedunsubstituted or hydroxyl-substituted C₂ -C₁₂ alkylene, cyclohexylene orphenylene, and R₇ and R₈ are each independently of the other chloro orbromo, phenyl or C₁ -C₄ alkyl, or R₇ and R₈, when taken together, aretrimethylene, ##STR9## Such polymers are disclosed, for example, in U.S.Pat No. 4,193,927.

The photopolymerisable or photodimerisable substances can containfurther additives customarily used for processing or application, aswell as other photoinitiators or photosensitisers.

The cationically curable systems are preferably epoxy compoundscontaining at least two epoxy groups in the molecule and in which aphotoinitiator is incorporated. Suitable photoinitiators are typicallycyclopentadienylarene metal salts, cyclopentadienyl metal carbonyl saltsand onium salts which are described in the above mentioned publications.The curable systems may contain additives customarily used forprocessing and application.

Photosensitive polyimides are disclosed, for example, in DE-A-1 962 588,EP-A-0 132 221, EP-A-0 134 752, EP-A-0 162 017, EP-A-0 181 37 and EP-A-0182 745.

The composition of this invention is applied by known methods as layerto substrates and either a protective layer is produced by irradiationover the surface, or a relief image is produced by irradiation through aphotomask or by locally defined irradiation with a guided laser beam orby holographic methods and subsequent development.

In another of its aspects, the invention relates to a compositioncomprising

a) a colourless organic solvent, a polymer or an organic glass or acompound glass, and

b) dissolved, incorporated therein or present as layer on at least onesurface, a compound of formula I or V or a mixture thereof. Component b)is preferably present in an amount of 0.001 to 20% by weight, preferably0.001 to 10% by weight and most preferably, 0.01 to 5% by weight, basedon component a). Organic solutions can be used for coating othersubstances, for example solid substrates such as inorganic glasses whichcan then be used as photochemically modifiable substrates. The compoundsof formula I can also be sublimed on to substrates. The coatedsubstrates can be provided with a protective layer of, for example,transparent polymers. Solid substrates can also be coated withcompositions which contain a polymer and at least one compound offormula I or V. Suitable solvents are typically hydrocarbons,halogenated hydrocarbons, ketones, carboxylic acid esters and lactones,N-alkylated acid amides and lactams, alkanols and ethers.

Exemplary of suitable polymers are thermoset plastics, thermoplasticsand structurally crosslinked polymers. The polymers axe preferablytransparent. Such polymers and organic glasses are known to thoseskilled in the art. The incorporation of the compounds of the inventionis effected by known methods, for example by dissolving methods andremoving the solvent, calendering or extrusion. The compounds of thisinvention can also be incorporated in the substrates before, during orafter their synthesis.

The invention also relates to a process for the preparation of colouredmaterials under the influence of light, which comprises incorporating acompound of formula I or V in the material and then irradiating saidmaterial with light.

The invention further relates to the use of compounds of formula I asphotosensitisers and colour indicators or photochemically modifiablecolour filters under the influence of light.

In yet another of its aspects, the invention relates to the use of acompound of formula I or V for the reversible optical storage ofinformation, which information is written with light, preferably laserfight, into a memory-active layer containing said compound. The writteninformation can be erased, preferably with laser light, thus affordingthe possibility of cyclic writing-in and erasing.

To produce a memory-active layer, the compound of formula I or V can bedissolved in a transparent matrix by methods desribed above and appliedin a thin layer to a flat substrate. The thickness of the memory-activelayer is ca. 0.1-100 μm, preferably 0.3-3 μm.

The information can be written by scanned, holographic or photographicirradiation of the memory-active layer with spectral, preferablycoherent, laser light in the wavelength range of 440-550 nm, preferably480-530 nm.

Reading out can be effected with reduced irradiation intensity at thewavelength in which the information is written via the locally alteredtransmission, reflectance, refraction or fluorescence of thememory-active layer.

Erasure can be made by pin-point or spread irradiation of thememory-active layer containing the compounds of formula I and/or V inthe wavelength range of 300-450 nm, preferably 300-420 nm.

One advantage of the utility of this invention is that the wavelengthsnecessary for writing in, reading out and erasing are in the range ofcommercially available lasers (for example argon ion lasers: 488/514 nmand 351/363 nm; neodym-YAG lasers: 532 nm and 355 nm with frequencydoubling and trebling; XeF excimer lasers: 351 nm; HeCd lasers: 325 and442 nm).

A further advantage is the high contrast of absorption obtainablebetween the written and erased state in the range of 450-550 nm and thewide dynamic range associated therewith of the memory-active layer.

Another advantage is that the quantum yield when writing is fairly low,so that the danger of overwriting when reading out is greatlydiminished.

Conversely, it is also advantageous that the quantum yield when erasingis fairly high, thus making possible a rapid erasure over a large area.

Yet a further advantage is that, when reading out, the compoundfluoresces and hence makes possible a highly sensitive detection of thememory status via the fluorescence. The fact that the energy pulsed infor reading out dissipates substantially via the fluorescence and notthermally also counteracts an undesirable heating of the memory-activelayer.

Another advantage is the high photochemical stability of the compoundand the great number of writing/erasing cycles thereby obtainable.

Finally, yet another advantage is the possibility of cyclic datarefreshing by admixture of a suitable quantum of light of the erasurewavelength during reading out.

The invention is illustrated by the following Examples.

A) Preparation of the starting compounds

EXAMPLE A1

2,3,6,8,9,11-Hexachloronaphthacene-5,12-dione.

30 g (70 mmol) of2,3,8,9-tetrachloro-6,11-dihydroxynaphthacene-5,12-dione, 60 ml of POCl₃and 500 ml of o-dichlorobenzene are stirred for 90 hours under reflux.Excess POCl₃ is distilled off, together with the o-chlorobenzene, untilthe reaction volume is still about 300 ml. The precipitate is isolatedby filtration from the cooled reaction mixture, washed repeatedly withwater and aqueous sodium carbonate solution and dried. The dry productis stirred in cyclohexane, isolated by filtration and then dried, givinga yield of 28.6 g (88 %), melting point (mp): >260° C.

EXAMPLE A2

2-Fluoro- and 9-fluoro-6,11-dichloronaphthacene-5,12-dione (mixture ofisomers).

3.0 g (9.73 mmol) of 2- and9-fluoro-6,11-dihydroxynaphthacene-5,12-dione (mixture of positionisomers), 4 ml of POCl₃ and 30 ml of o-dichlorobenzene axe stirred for10 hours under reflux. The reaction mixture is poured into water andneutralised with 2 N aqueous NaOH. The precipitate is isolated byfiltration, washed with water, dried, taken up in 400 ml of toluene.After addition of basic alumina, the batch is filtered hot. The filtrateis concentrated by evaporation, giving 1.57 g (47%) of the productmixture. Mass spectrum: 344, 346, 348 and 350 (M⁺ : base peak).

B ) Preparation of the inventive compounds

EXAMPLE B1

2,3,8,9-Tetrachloro-6,11-diphenoxynaphthacene-5,12-dione. 2.32 g (5mmol) of the compound of Example A1, 1.41 g (15 mmol) of phenol, 4.15 g(30 mmol) of potassium carbonate and 100 ml of tetrahydrofuran areheated for 5 hours under reflux. The mixture is poured into water, withstirring, and then filtered. The precipitate is washed first with waterand then with methanol/water, dried, and then recrystallised fromo-dichlorobenzene, affording the title compound in a yield of 2.57 g(89%) in the form of yellow crystals with a melting point of 326°-329°C. Mass spectrum 578/580/582 (M⁺ : base peak).

When irradiated, a solution of the compound in toluene undergoes areversible colour change from yellow to orange.

EXAMPLE B2

2,3,6,8,9,11-Hexaphenoxynaphthacene-5,12-dione.

1.5 g (3.2 mmol) of compound A1, 2.43 g (25.8 mmol) of phenol, 4.45 g(32.3 g) of potassium carbonate and 120 ml of N-methylpyrrolidone arestirred for 8 hours at 150° C. The mixture is taken up intetrahydrofuran/toluene/2 N hydrochloric acid and the organic phase isseparated, washed with water, dried over sodium sulfate and thenconcentrated by evaporation. The crude product is dissolved in tolueneand chromatographed over silica gel, affording the title compound in ayield of 0.65 g (25%) in the form of yellowish-orange crystals.

Mass spectrum: 810 (M⁺ : base peak). When irradiated, a solution of thecompound in toluene undergoes a reversible colour change fromyellowish-orange to red.

EXAMPLE B3

Mixture of 2,6,11- and 6,9,11-triphenoxynaphthacene-5,12-dione.

0.5 g (1.45 mmol) of compound A2, 0.8 g (5.8 mmol) of potassiumcarbonate, 0.48 g (5.07 mmol) of phenol and 5 ml of dimethyl sulfoxideare stirred for 4 hours at 100° C. The reaction mixture is poured intodilute hydrochloric acid and extracted with tetrahydrofuran/toluene(1:1). The extracts are washed with saturated aqueous NaCl and water,dried over sodium sulfate and concentrated by evaporation.Recrystallisation from toluene gives 0.58 g (75%) of the title compoundof m.p.: 220°-23° C. Mass spectrum: 534 (M⁺ : base peak).

When irradiated, a solution of the compound in toluene undergoes areversible colour change from yellow to orange.

C) Use Examples

EXAMPLE C1

2.5 g of polystyrene are dissolved in 15 ml of toluene at 60° C. underargon.

To this solution are added, after 20 minutes, 25 mg of the compound ofExample B1, and the mixture is stirred for 20 minutes. The solution isapplied with a 200 μm doctor knife at 80° C. to a glass plate and thendried for 60 minutes at 80° C., to give a transparent film having athickness of about 30 μm. The film is mounted on a quartz plate in thetesting chamber of a spectrophotometer and irradiated with a 300 W xenonlamp through glass fibres and a UV filter. The irradiation isdiscontinued at 60 second intervals and the absorption spectrum ismeasured. The spectrum of the sample changes from yellow (opticaldensity 1 at about 320 nm, 0.4 at about 400 nm and 0 above 450 nm) tored (absorption band in the range from about 400-450 nm; maximum opticaldensity 0.65 at 480 nm). The time constant of the conversion is 140seconds. For the reverse reaction, the UV filter is replaced by a yellowcut-on filter (Schott GG 455). The integral irradiation intensity in therange from 430-540 is 3 mW/cm². The irradiation causes the long-waveabsorption band to disappear at 400-450 nm to a maximum optical densityof 0.2 at 480 nm. The time constant of the reverse reaction is 110seconds. In further irradiation cycles these critical values of theoptical density remain constant.

EXAMPLE C2

The general procedure of Example C1 is repeated, except that thecompound of Example B2 is used. The spectrum changes from yellow(optical density 1 at about 340 nm, 0.35 at about 400 nm and 0 above 450nm) to red (maximum absorption 0.6 at 480-510 nm) with a time constantof 180 seconds. The time constant of the reverse reaction (irradiationintensity 2.5 mW/cm²) is 160 seconds (maximum optical density 0.15 at480 nm).

What is claimed is:
 1. A composition which comprises(a) a substratewhich is a colorless organic solvent, a polymer, an organic glass or acompound glass; and (b) a compound of the formula I or a mixture thereof##STR10## wherein R is unsubstituted C₆ -C₁₄ aryl or C₆ -C₁₄ aryl whichis substituted by C₁ -C₁₂ alkyl, C₁ -C₁₂ alkoxy, C₁ -C₁₂ alkylthio,phenyl, benzyl, --CN, --CF₃, halogen or --COOR₅, and R₅ is H, C₁ -C₁₈alkyl, cyclohexyl, cyclopentyl, phenyl, C_(1-C) ₁₂ alkylphenyl, benzylor C₁ -C₁₂ alkylbenzyl, and at least one of the substituents R₁ to R₄ is--F, --Cl or --Br, or is independently the group RO--, and the othersubstituents R₁ to R₄ are H, --F, --Cl or --Br; which compound offormula I is dissolved in the substrate, incorporated in the substrate,or present on at least one surface of the substrate.
 2. A compositionaccording to claim 1, wherein R in formula I is unsubstituted orsubstituted C₆ -C₁₀ aryl.
 3. A composition according to claim 2, whereinR is unsubstituted or substituted phenyl or 1- or 2-naphthyl.
 4. Acomposition according to claim 1, wherein R in formula I isunsubstituted or substituted by C₁ -C₄ alkyl, C₁ C₄ alkoxy, C₁ -C₄alkylthio, --F, --Cl, --Br or --COOR₅, wherein R₅ is H or C₁ -C₁₈ alkyl.5. A composition according to claim 1, wherein at least one of thesubstituents R₁ to R₄ in formula I is a group RO-- or --F, --Cl or --Br,and the other substituents R₁ to R₄ are H.
 6. A composition according toclaim 1, wherein R₁ or R₄, or R₁ and R₃ or R₄, or R₁ and R₂ or R₂ to R₄is a group RO--, --F, --Cl or --Br.
 7. A composition according to claim1, wherein R₁ or R₄, or R₁ and R₃ or R₄, or R₁ and R₂ or R₁ to R₄ is agroup RO-- or --Cl.
 8. A composition according to claim 1, wherein R isunsubstituted phenyl.
 9. A composition according to claim 1, wherein thecompound of formula I is selected from the group consisting of6,11-diphenoxy-2-chloronaphthacene-5,12-dione,2,6,11-triphenoxynaphthacene-5,12-dione,6,11-diphenoxy-2,3,8,9-tetrachloroaphthacene-5,12-dione and2,3,6,8,9,11-hexaphenoxynaphthacene-5,12-dione.
 10. A composition whichcomprises(a) a colorless substrate which is an organic solvent, apolymer, an organic glass or a compound glass; and (b) a compound of theformula V or a mixture thereof ##STR11## wherein R is unsubstituted C₆-C₁₄ aryl or C₆ C₁₄ aryl which is substituted by C₁ -C₁₂ alkyl, C₁ -C₁₂alkoxy, C₁ -C₁₂ alkylthio, phenyl, benzyl, --CN, --CF₃, halogen or--COOR₅, and R₅ is H, C₁ -C₁₈ alkyl, cyclohexyl, cyclopentyl, phenyl, C₁-C₁₂ alkylphenyl, benzyl or C₁ -C₁₂ alkylbenzyl, and at least one of thesubstituents R₁ to R₄ is --F, --Cl or --Br, or is independently thegroup RO--, and the other substituents R₁ to R₄ are H, --F, --Cl or--Br; which compound of formula V is dissolved in the substrate,incorporated in the substrate, or present on at least one surface of thesubstrate.